The present invention is directed to an accumulating conveyor upon which articles may be stored or accumulated to be advanced to a work station only when the work station is ready to receive an article.
A typical application of such a conveyor is in a production line where, due to the nature of an operation performed on the article at the work station, the rate at which articles are discharged from the work station is a variable rate or a rate which is less than the rate at which articles can be supplied to the work station. When the work station is occupied, the conveyor functions to halt the flow of articles to the work station, thus accumulating a line of articles upstream from the work station so that articles can be supplied to the work station as fast as the work station is ready to accept them. The basic requirement of such a conveyor is that it must be able, while being continuously operated, to advance articles intermittently in accordance with the requirements of the work station.
In the prior art, a walking beam type conveyor is conventionally used to perform the foregoing function. Uniformly spaced article receiving seats are located along the fixed frame of the conveyor and a lift-and-carry mechanism is associated with each seat which is operable in a cyclic sequence to lift and carry an article from one seat to the next advanced seat to advance the articles in step-by-step movement along the conveyor. The various lift-and-carry mechanisms are interlinked with each other so that only those lift-and-carry mechanisms which are upstream from an empty seat will be actuated to advance articles in an operating cycle. Prior art examples of such conveyors are found in U.S. Pats. Nos. 4,441,606 and 4,240,542.
While the walking beam type accumulating conveyor is widely used, it possesses certain inherent drawbacks. A lift-and-carry mechanism must be provided at each station, together with a sensing mechanism at each station which detects the presence or absence of a part or article at that station to signal all upstream stations as to whether they are to act in the transfer or nontransfer mode during the next cycle. The intermittent step-by-step operation relies upon a reciprocatory drive mechanism which subjects a multitude of interconnected system parts to impact loading at stroke reversal and which is subjected to a variable loading, depending upon the number of parts which are to be advanced, upon the actuating stroke. The articles conveyed in turn must be bodily lifted from the conveyor frame, advanced, and then lowered gently back onto the conveyor frame a substantial number of times in order to transit the conveyor.
The present invention overcomes the foregoing problems by employing a continuously driven roller chain conveyor on which are mounted a plurality of article carriers which are so mounted upon the chains they may either move with or relative to the chains so that a carrier may be stopped at any desired location along a horizontal run of the chain while the chain continues to move.